Use of food and space by white rhinos

Abstract:

The manner in which herbivores respond to seasonal changes in the quality and availability of food resources is dependant on the herbivores' body size and digestive system. This study focused on how seasonal changes in the quality and availability of food resources influenced the foraging behaviour and movement of free ranging white rhinoceroses (body mass exceeding 1000 kg) in the Hluhluwe- Umfolozi Park, South Africa. Body size theory suggests that, because large herbivores tolerate lower quality food better than small herbivores, white rhinos should be relatively unselective grazers, selecting grassland types rather than grass species. In accordance with this prediction, it was found that white rhinos selected mainly for grassland types throughout the study period. However, despite being non-ruminants of very large body size, white rhinos primarily fed on short to intermediate height swards of green grass throughout most of the study period.<br><br> The foraging of large herbivores can be seen as a trade-off between diet quality and quantity. To determine the trade-offs made by white rhinos during the dry season, the author compared seasonal changes of dry matter intake and the intake of specific nutrients. As the greenness and nutrient content of grass declined late in the dry season, white rhinos responded by increasing their dry matter intake. Despite this response, the intake of crude protein, P and Na declined throughout the dry season. The author suggests the possibility that instead of compensating for declines in nutritional gain through the adjustment of dry matter intake, white rhinos rely on fat reserves to help maintain them during periods of low food quality and availability.<br><br> A novel discovery of the study was that large scale movements, and possibly dispersal, of subadults, may be facilitated by individuals following companions or 'buddies' (either adult females or other subadults) into novel areas. This "buddy system" may be important in reducing the high costs potentially associated with dispersal.